Changeable combination cylinder lock

ABSTRACT

A cylinder lock in which the tumbler assemblies can be rotated with respect to one another by means of a combination-change key to change the combination of the lock for various unlocking keys. The tumbler assemblies have mating cam projections and recesses whereby the assemblies can be positioned and rotated with respect to each other.

PA'I'EMED JUH 1 IS?! INVENTOR FRANK J. TESTA BYZOW'MM ATTORNEYS WINDOWLOCK BACKGROUND OF THE INVENTION the lock unit 26 is in one of itslocking positions the tumbler 50, 50 project beyond the cylindricalsurface of the plug 34 and into an associated one of the recess 48, 48.The tumblers are adapted for retraction into the plug 34 from their pro-This invention relates in general to locking devices for win- 5 lectedposition5 3cm)" Ofa P p y 54 inserted in a dows and the like and dealsmore particularly with an improved locking device for a windowofdouble-hung sash type.

The general aimof the present invention is to provide an improvedlocking device of the aforedescribed type for locking in a plurality ofpositions to retain a window in a closed position or to permit thewindow to be moved freely between closed and partially opened positions.

SUMMARY OF THE INVENTION In accordance with the present invention awindow-locking device is provided which includes strike means formounting on one part of a window and a strike-engaging element formounting on another part of the window and lockable in a plurality ofpositions relative to the strike means for selectively locking a windowin a closed position or in one or more other positions wherein thewindow is movable freely between closed and partially opened positions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary elevationalview ofa window having double-hung sash showing a locking deviceembodying the present invention mounted thereon.

FIG. 2 is a fragmentary sectional view taken along the line 2-2 of FIG.1.

FIG. 3 is a sectional view through the lock unit taken along the line3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to thedrawing, a locking device embodying the present invention and indicatedgenerally at is shown mounted on a double-hung window which has upperand lower sash indicated at 12 and 14, respectively, slidable in a frame16 between open and closed positions. The upper sash has a side rail 18and a bottom crossrail 20 and the lower sash includes a side rail 22 anda top crossrail 24. The two crossrails are in contactwhen the window isin a closed position as it appears in FIG. 1.

The locking device 10 comprises a lock unit indicated generally at 26mounted on the upper surface of the crossrail 24 and strike plates 28and 30 fastened to the side rail 18 which cooperate with the lock unitin various locking positions to lock the window in a closed position orto limit its movement between closed and partially opened positions.

Considering first the lock unit 26, the unit generally comprises acasing 32 supporting a rotary or locking element 34 which carries alocking member 36. The casing may be made in various forms butpreferably, and as shown, it includes a barrel portion 38 and agenerally rectangular base flange 40 which has a rectilinear edge 42 forparallel alignment with the crossrail 24 to aid in positioning the lockunit on the sash 14. A generally cylindrical bore 44 extends through thebarrel portion 38 and has an axis 46 disposed in a plane generallyparallel to the plane of the base flange. As viewed from above in FIG.2, the axis 46 is inclined with respect to the rectilinear edge 42 andthe plane of the sash. Recesses 48, 48 extend longitudinally of the bore44 at the top, bottom and opposite sides thereof, respectively, as shownin FIG. 3.

The locking element used in practicing the invention may be of any typesuitable to cooperate with the casing in a plurality of lockingpositions. In the illustrated embodiment 10 the locking element 34 is aconventional cylindrical key plug of disc tumbler type which has anaxially spaced series of disc tumblers mounted in radial slots therein,a typical tumbler being indicated at 50 in FIG. 3. A spring 52 isoperatively assoeiated with each tumbler 50 to bias the tumbler towardand to resiliently hold it in a projected position as shown. When slotopening through the forward end of the plug. When the tumblers arcretracted the plug 34 may be rotated in the bore 44 by the key 54.

The strikeengaging member 36 is generally L-shaped and is riveted orotherwise suitably secured at one end to the rear end of the plug 34 andserves to retain the plug in assembly with the casing 32. The terminalor free end portion of the member 36 is spaced radially outwardly fromthe axis 46 and bent rearwardly. It has an arcuately formed radiallyoutwardly facing strike engaging surface 56 and abutment surface 58 and60 on opposite sides thereof arranged to engage the upper surface of thebase flange 40 which limits rotation of the plug 34 in both a clockwiseand a counterclockwise direction.

The number of locking positions may vary. The illustrated device 10 hasthree locking positions which include an inoperative position and twooperative ones. In FIG. 1, the member 36 is shown in 12 o'clock positioncorresponding to a fully locked position of the window. The disctumblers 50, 50 are aligned with recesses 48, 48 at the top and bottomof the bore 44 and biased downwardly into the recess 48 at the bottom ofthe bore when the key 54 is withdrawn from the plug to retain the lockunit 26 in the latter position. Rotation of the key 54 in acounterclockwise direction from the fully locked position moves themember 36 to a nine Oclock or inoperative position. The abutment surface58 engages the flange 40 to arrest counterclockwise rotation of the plugwhen the tumblers 50, 50 are generally aligned with the recess 48, 48 atthe sides of the bore so that the key 54 may be withdrawn to lock themember in its nine oclock position. Rotation of the key in a clockwisedirection through an angle of from the inoperative position moves themember 36 to another operating position at three oclock corresponding toanother locked condition of the window. Clockwise rotation of the plug34 is arrested by engagement of the abutment surface 60 with the baseflange 40 as best shown in FIG. 3. The key may also be withdrawn fromthe plug to lock the unit 26 when the locking member 36 is in its threeoclock position.

The strike plates 28 and 30 are fastened to the side rail 18 invertically spaced relation to each other and to the crossrail 20 andpreferably extend for some distance inwardly from the rail or toward thecenter of the window. The lower strike plate has a downwardly facingabutment surface 62 for engaging the arcuate surface 56 on the member 36when the window is in its closed position and the lock unit is in itsfully locked position. The upper strike plate 30 extends inwardly forsome distance beyond the lower strike plate 28 and has a downwardlyfacing abutment surface 64 for engaging the side abutment surface 58when the member 36 is in its three o'clock position. In the latterposition the terminal end portion of the member 36 is disposedtransversely inwardly of the inner edge of the lower strike plate 28 sothat the member 36 is free to move past the strike plate 28 as thewindow is moved toward its open position. The inwardly extending freeend portion of the upper strike plate 30 is disposed in the path of theelement 36 so that the abutment surface 58 ultimately engages thestrikeengaging surface 64 to limit the movement of the window toward itsfully open position. Thus, when the element 36 is locked in its threeoclock position the sash 12 and] 14 are freely movable between theirclosed position and partially open positions. When the element 36 is inits inoperative position, the terminal end of the element is spacedforwardly of the strike plates 28 and 30 and the sash l2 and 14 arefreely movable between their closed and fully opened positions lclaim:

l. A locking device for a window having double'hung sash longitudinallymovable relative to each other through a range of positions betweenopened and closed positions, said device comprising strike means adaptedfor mounting in fixed posi- BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to the field of cylinder locks in whichthe lock combination can be varied without disassembling the entirelock.

Throughout this specification the term combination" refers to theunlocking formula peculiar to a given set of tumbler assemblies and thecorresponding indicia on the particular unlocking key which operatesthat set of tumbler assemblies. The term cylinder lock" refers to akey-operated mechanism that operates ancillary devices such as a boltand latch to bring the-bolt and latch into and out of lockingengagement.

2. Description of the Prior Art Changeable combination locks areparticularly desirable in situations where a number of persons haveaccess to the keys for sufficient periods of time to permit the keyprofile to be copied. Obviously a copy of a key can be used to open thelook as well as the original unlocking key. If, however, the lockcombination can be varied from time to time, unauthorized access bymeans ofa copied key can be significantly thwarted.

Cylinder locks which have changeable combinations are well known in theart. US. Pat. No. 2,766,61 l reveals a cylinder lock which can bedisassembled to change the combination. Once the lock is disassembled,one of the tumblers is inverted with respect to the others and the lockis reassembled with a new combination.

It is desirable to be able to vary the lock combination without havingto disassemble the entire cylinder assembly. Locks of this type areknown from US. Pat. Nos. 2,603,081 2,895,323 and 3,263,461.

US. Pat. No. 3,263,461 is of particular interest in that it discloses alock frequently used in parking meters wherein the combination can bechanged without disassembly. In that patent the tumbler assemblies arerotated with respect to one another by means of a combination-change keyto change the combination and thereby adapt the lock to one of aplurality of unlocking keys. However, the prior-art lock of this patentemploys sliding tumblers which engage adjacent tumbler assemblies tohelp prevent relative rotation ofone tumbler assembly with respect tothe others if the tumblers should inadvertently slide from theirunlocked positions, and this construction results in several significantdisadvantages. For example, the tumblers must be returned to a startingor base position before a new combination can be set, thereby requiringthe use of several change keys. Also, it can only be mountedhorizontally.

SUMMARY OF THE INVENTION The present invention relates to an improvedchangeable combination cylinder lock. The combination of the lock ischanged by means of combination-change keys and is accomplished bychanging the relative positions of the tumbler assemblies with respectto one another.

The tumbler assemblies are composed of a carrier element and tumblersbearing indicia of the lock combination. The assemblies and theiraccessories are serially mounted along a cylinder axis to form the coreof the cylinder lock. The assem' blies are normally coupled together bymeans of axially extending camming portions on the tumbler retainers andthe specific locking function is provided by sliding any one of thetumblers within the assemblies into engagement with longitudinal cutoutsin the lock casing. A spring element normally biases the cammingportions of the adjacent tumbler assemblies into engagement. When thelock combination is to be changed a combination-change key cooperateswith the camming portions to rotate the tumbler assemblies with respectto one another.

The camming portions are formed by triangularly shaped teeth whichengage mating recesses at the confronting surfaces of adjacent tumblerassemblies. The teeth are positioned apart near the periphery of theassemblies and permit the assemblies to engage one another in twodifferent relative positions to form different lock combinations.

The tumblers themselves slide within the tumbler assem blies and theindicia-bearing portion of the tumblers project within a centrallylocated keyhole channel formed by the as semblies. Since the assembliesare rotated 180 with respect to one another to vary the lockingcombination, two tumblers symmetrically located with respect to thecentral keyhole channel may be carried in each assembly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of mycylinder lock with a key and bolt in position.

FIG. 2 is a cross-sectional view of the assembled cylinder lockinstalled in a working environment.

FIG. 3 is a cross-sectional view of the cylinder lock between adjacenttumbler assemblies looking toward the bolt with a key in unlockingposition.

FIG. 4 is an exploded view of the elements forming the core assembly ofmy cylinder lock.

FIG. 5 is an end view of the tumbler retainer as viewed from the rightin FIG. 4.

FIG. 6 is a view of the tumbler assemblies during a combination-changingsequence.

Like reference numerals are used throughout the drawings where likeelements are shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference to FIGS. 1 and 2shows my cylinder lock, generally designated by numeral 10, with a bolt12 and an installed key K. As seen in FIG. 2 the lock 10 can beinstalled in a housing 14 by means ofa collar 16 and jamnut 18. Thehousing 14 may be that ofa parking meter change box. The bolt 12 isshown in locking position with a latch 20 which would be permanentlyconnected with a fixed portion of the parking meter. The bolt 12 is heldto the cylinder lock by means of a nut 22 and rotates with the lock coreassembly by means of flats on the stub shaft 24.

The lock 10 is composed basically ofa casing and a core assembly. Thecasing is formed by a barrel 26 and a cap member 28 crimped on thebarrel 26 after the core assembly has been installed. The internalsurface 38 of the barrel 26 is cylindrical and includes fourlongitudinal cutouts 40.

The core assembly is composed of a plurality of tumbler assemblies 30(letter suffices being used where necessary to distinguish the similarassemblies and their subparts), a thrust plate 32, a thrust spring 34,which takes the form of a fluted washer, and an end plate 36. In theassembled lock the core assembly is essentially sandwiched between thebarrel 26 and cap 28 by the thrusting force of spring .34.

The locking function is performed by the tumbler assemblies 30 andcutouts 40. As seen in FIGS. 3 and 4 each tumbler assembly 30 iscomposed of a tumbler retainer 42 and two symmetrically positionedtumblers 44, 46. The tumblers 44, 46 slide freely within grooves 48, 50in the retainers 42. The cutouts 40 in the barrel 26 are located in thecylindrical sur face 38 to register in the locking position with thegrooves 48, 50 in the retainers 42. The cutouts 40 have the same widthas the grooves 48 and 58 in the retainers 42. This positioning and sizeof the cutouts 40 pennit the tumblers 44, 46 to slide into the cutouts40 and lock the tumbler assembly 30 to the barrel 26. The tumblerassemblies are coupled together by cams-and recesses as described belowand consequently the engagement of any one of the tumblers 44, 46 withthe cutouts 40 will prevent rotation of both the lock core assembly andthe bolt 12 rigidly fastened to the stub shaft 24 on the inner tumblerassembly 300.

Each of the tumbler retainers 42 includes a centrally located keychannel 52 seen in FIG. 3 through which a key K may be inserted tooperate the tumblers. The channel in the innermost retainer 42c may be ablind channel since it is not necessary for the key to project entirelythrough the stub shaft 24 and bolt 12. Each of the tumblers 44, 46includes a central portion having a key follower 54, 56 respectively.These followers 54, 56 project into the key channel 52 and engagelaterally disposed camming grooves cut in opposite faces of the key K.It will be understood that the camming grooves in the key K if properlycut for the tumblers 44, 46 will lift the tumblers out of the cutouts 40in the barrel 26 as shown in FIG. 3 and will permit the tumbler assembly30 to rotate with respect to the barrel 26. The positioning of thefollowers 54, 56 on the tumblers 44, 46 are therefore indicia of theparticular combination for unlocking the respective tumblers. With aplurality of tumbler assemblies 30 forming the core assembly it will benecessary that the camming grooves in the appropriate unlocking key beprecisely located to lift all of the tumblers out of the cutout 40 whenthe key is completely inserted. With all tumblers lifted, the key canrotate the core assembly and consequently the bolt 12 with respect tothe fixedly mounted barrel 26.

it will be readily understood that a multitude of lock combinations canbe formed from this lock design with three or four standard tumblersdiffering only in the positioning of the followers on the centralportions. Thousands of different combinations may be fonned bydisassembling the lock, rearranging the tumbler assemblies in differentorders and rearranging the tumblers within the various tumblerassemblies.

The combination of the cylinder lock may also be changed withoutdisassembly simply by rotating one tumbler assembly with respect to theothers. This rotation is accomplished by means of a combination changekey which engages the followers 54, 56 in precisely the same manner asthe unlocking keys except that a combination key only engages thosetumbler assemblies which must be rotated to change to a particular newcombination. For example, if tumbler assembly 30b is to be inverted orrotated 180 with respect to assemblies 30a and 30c, two change keyswould be employed. The first change key would engage and lift only thetumblers in assemblies 30a and 30b. This would ermit the assemblies 300and 30b to be rotated with respect to assembly 300. A second change keywould then be used to engage and lift only the tumblers in assembly 30aso that assembly 30a would be rotated back to its original position withrespect to assembly 300. The inversion of tumblers 44b, 46b with thefollowers 54b, 56b will now form a new combination with the adjacenttumblers.

A particularly important feature of my invention is the design of thetumbler assemblies which always permits rotation of the outer tumblerassemblies with respect to the inner tumbler assemblies regardless ofthe existing lock combination. As seen most clearly in FIG. 4 theretainers 42 include camming tangs 60 in the form of triangularly shapedteeth and mating cam recesses 62 alternately located on the axiallyconfronting surfaces of the retainers. The camming tangs 60 extendaxially from the confronting surfaces and are located at positions 180-apart on the cylindrical tumbler retainers 42. The recesses 62 extendaxially into the retainers 42 and are similarly positioned 180 apart asmost clearly seen in FIG. 5. Tangs 60 and recesses 62 are normallyengaged and held engaged by the thrusting force of the thrust spring 34applied serially through the thrust plate 32 and the retainers 42. Whena change key causes one or more of the outer tumbler assemblies to berotated, the inner assemblies are locked to the barrel 26 by means ofthe tumblers 44, 46 and camming action of the tangs 60 and recesses 62causes a slight axial displacement and disengagement of the outer,rotated tumbler assemblies from the inner assemblies. Since the entirecore assembly is sandwiched between the barrel 26 and the cap 28,compliance is necessary to permit the axial displacement of a tumblersembly and is provided by the spring 34.

Reference to FIG. 6 shows the axial displacement of assembly 30a withrespect to assemblies 30b and 30c which oc curs during the use of thesecond change key in the example cited above. As shown, the cammingaction between tangs 60b and the recess 62a has displaced assembly 30aaxially along with the thrust plate 32. The apex of tang 60b will slideon the periphery of assembly 30a until the camming recess 620 haverotated and are aligned with the diametrically opposite tangs.

It will be noted that during relative rotation of the assemblies, springthrust will cause the tangs 60b to bear against the confronting surfaceof assembly 3011. To assure that no binding occurs during this step, theconfronting surface of assembly 30a is smooth along its periphery exceptfor the recesses 62. For this reason the grooves 48, 50 which guide thetumblers 44, 46 are always located in the same confronting surface whichincludes the tangs 60. ll is also to be noted that the rotation of theassemblies for combination change is al ways in one direction (clockwiseas presently illustrated) and the flat of each tang against the wall ofthe recess prevents movement in the other direction.

The tumblers 44, 46 are prevented from rotating in the grooves 48, 50 bythe flatted sides and the thickness between the axially opposite sidesshould preferably be less than the depth of the grooves to prevent thetumblers from catching on the recesses 62. Of course, it is possiblethat the tumblers could be carried in transverse holes lying whollywithin the retainers. In such case, the relationship of the tangs andrecesses with respect to the tumblers need not be so rigidly defined.

My improved cylinder lock offers several advantages which are notavailable in the prior-art locks.

Since the position of the tumblers within the tumbler assemblies 30 doesnot interfere with the rotation of an outer tumbler assembly withrespect to the inwardly adjacent assembly, my lock can be mounted ineither a horizontal or a vertical position without fear of adjacentassemblies becoming locked together due to a shifting or intentionalpositioning of one tumbler in an inwardly disposed assembly. Thetumblers do not interfere with changing the lock combination because theengagement of adjacent tumbler assemblies is not provided by thetumblers, but instead, by the retainers 42. Another advantage closelyassociated with the intercoupling by means of the retainers is the factthat changing a given combination requires a smaller number of changekeysv For example, if the intercoupling of adjacent tumbler assemblies30b and 30c were provided by the tumblers 44c, 46c it might be necessaryto first disengage the tumblers 44c, 46c from assembly 30b beforeassembly 30b could be rotated with respect to assembly 30c. Thisrequires at least one additional change key and in other situations morethan one additional change key may be required to make the desiredcombination change.

Additionally, it willbe noted that the camming tangs 60 and recesses 62normally lock all of the tumbler assemblies 30 together. With any singletumbler engaged in the barrel cutouts 40, the entire core assembly willremain continuously locked to the barrel 26. The interlocking of thevarious tumbler assemblies eliminates any problems of one assemblyinadvertently rotating with respectto another in the event that thetumblers of an outer assembly, for example 30a, become disengaged fromthe cutouts 40 of barrel 26. It will be understood that such inadvertentrotation might occur during shipping and would change the previouslyestablished lock combination to a new and unknown combination. Lockinserts are used in the prior-art devices to prevent such inadvertentrotation of the tumblers; however, with my improved lock such insertsare not essential.

In the prior-art locks which rely upon specially shaped tumblers toengage adjacent tumbler assemblies it is possible that the tumblers canbe damaged in the event that the wrong change key is used when setting anew combination. By eliminating the specially shaped tumblers and usingspringloaded camming portions, such damage is precluded. Furthermore,the shape of my tumblers renders them simple and more economical tomanufacture.

lt will be understood that various modifications can be made to thespecific structure shown and described. For example, the number ofpossible lock combinations can be greatly multiplied by using more thanjust three tumbler assemblies 30. The camming tangs 60 and the matingrecesses 62 need not take the form of ratchet teeth but may with equalfacility take a symmetric form having two camming surfaces to permitrelative rotation of the tumblers in either direction. lf desired, othercurved shapes rather than the triangular tooth may be employed providedthe cams maintain their locking function.

lclaim:

1. A core assembly for a changeable combination cylinder lockcomprising:

a plurality 'of cylindrical tumbler carriers coaxially positioned withrespect to one another and serially located along a core axis, thecarriers bearing axially confronting surfaces defining mated cammingtangs and tang-receiving portions forming disengageable couplingsbetween adjacent carriers;

resilient thrusting means axially contacting at least one carrier forurging the disengageable couplings of the carriers into engagement; and

a lock tumbler located in each tumbler carrier and freely slidable inthe carrier in a direction generally transverse to the core axis.

2. The core assembly of claim 1 wherein:

the confronting surfaces of tumbler carriers defining the camming tangsadditionally define a nesting groove extending generally transverse tothe core axis; and

the lock tumblers in the carriers having confronting surfaces definingthe camming tangs are slidably mounted within the nesting groove.

3. The core assembly of claim 2 wherein the tumblers are fitted inclose, sliding contact with the nesting grooves and have flat surfacesin contact with the grooves to prevent rotation of the tumblers in thegrooves.

4. The core assembly of claim 1 wherein:

the coaxially' positioned tumbler carriers define a centrally locatedkeyhole having a noncircular cross section; and

the freely slidable tumbler includes a central portion bearing indiciaof the lock combination and projecting at least partially within thecentrally located keyhole.

S. The core assembly of claim 1 wherein:

the camming tangs consist of two ratchet teeth extending from an axiallyconfronting surface of the rotatable retainer and spaced 180 apart nearthe periphery of the rotatable retainer.

6. An improved cylinder lock having changeable key combinationscomprising:

a lock casing having a cylindrical bore with tumbler receiving cutouts;

a plurality of rotatable tumbler retainers positioned coaxially withinthe cylinder bore of the casing in adjacent relationship and havingmatched and axially extending camming portions intercoupling adjacentretainers;

cam-engaging means operatively associated with the plurality of tumblerretainers for biasing the camming portions of adjacent retainers intoengagement; and

key-operated tumblers slidably mounted within the tumbler retainers andhaving locking sections shaped to slidingly mate with the tumblerreceiving cutouts of the lock casmg.

7. The cylinder lock of claim 6 wherein:

the surface of one retainer confronting with an adjacent retainerincludes a tumbler slot of preselected depth in the axial direction andextending lengthwise across the confronting surface; and

the key-operated tumbler within the retainer is slideably mounted in andsecured against rotation in the slot and has a thickness in the axialdirection less than the preselected depth of the slot.

8. The cylinder lock of claim 6 wherein:

the lock casing includes two pairs of longitudinal tumblerreceivingcutouts, the pairs bein respective] offset by equal amounts on oppositesides 0 a central p ane bisecting the cylindrical bore of the casing;

the rotatable tumbler retainers rotate concentrically about the axis ofthe cylindrical bore; and

two key-operated tumblers are slidably mounted in parallel relationshipwithin one rotatable retainer and are offset from the center of rotationof the retainer by an amount equal to the offset of thetumbler-receiving cutouts to register with the cutouts in a lockingposition of the retainer.

9. The cylinder lock of claim 6 wherein:

the rotatable tumbler retainers are generally cylindrically shaped withaxially opposed end surfaces; and

the camming portions of the rotatable tumbler retainers includetriangularly shaped and axially extending teeth and mating recesses onconfronting end surfaces of the tumbler retainers.

10. The cylinder lock of claim 9 wherein:

the cam-engaging means includes a spring element for resiliently biasingthe triangularly shaped teeth into engagement with the mating recesses;and

the end surfaces of the tumbler retainers bearing the triangular teethadditionally include a tumbler-guiding groove extending transverse ofthe cylindrically shaped retainers and having a depth in the axialdirection completely accommodating the tumblers within the grooves belowthe end surfaces whereby the tumblers may slide freely within thegrooves of the retainer when the teeth are engaged with the matingrecesses.

1. A core assembly for a changeable combination cylinder lockcomprising: a plurality of cylindrical tumbler carriers coaxiallypositioned with respect to one another and serially located along a coreaxis, the carriers bearing axially confronting surfaces defining matedcamming tangs and tang-receiving portions forming disengageablecouplings between adjacent carriers; resilient thrusting means axiallycontacting at least one carrier for urging the disengageable couplingsof the carriers into engagement; and a lock tumbler located in eachtumbler carrier and freely slidable in the carrier in a directiongenerally transverse to the core axis.
 2. The core assembly of claim 1wherein: the confronting surfaces of tumbler carriers defining thecamming tangs additionally define a nesting groove extending generallytransverse to the core axis; and the lock tumblers in the carriershaving confronting surfaces defining the camming tangs are slidablymounted within the nesting groove.
 3. The core assembly of claim 2wherein the tumblers are fitted in close, sliding contact with thenesting grooves and have flat surfaces in contact with the grooves toprevent rotation of the tumblers in the grooves.
 4. The core assembly ofclaim 1 wherein: the coaxially positioned tumbler carriers define acentrally located keyhole having a noncircular cross section; and thefreely slidable tumbler includes a central portion bearing indicia ofthe lock combination and projecting at least partially within thecentrally located keyhole.
 5. The core assembly of claim 1 wherein: thecamming tangs consist of two ratchet teeth extending from an axiallyconfronting surface of the rotatable retainer and spaced 180* apart nearthe periphery of the rotatable retainer.
 6. An improved cylinder lockhaving changeable key combinations comprising: a lock casing having acylindrical bore with tumbler receiving cutouts; a plurality ofrotatable tumbler retainers positioned coaxially within the cylinderbore of tHe casing in adjacent relationship and having matched andaxially extending camming portions intercoupling adjacent retainers;cam-engaging means operatively associated with the plurality of tumblerretainers for biasing the camming portions of adjacent retainers intoengagement; and key-operated tumblers slidably mounted within thetumbler retainers and having locking sections shaped to slidingly matewith the tumbler receiving cutouts of the lock casing.
 7. The cylinderlock of claim 6 wherein: the surface of one retainer confronting with anadjacent retainer includes a tumbler slot of preselected depth in theaxial direction and extending lengthwise across the confronting surface;and the key-operated tumbler within the retainer is slideably mounted inand secured against rotation in the slot and has a thickness in theaxial direction less than the preselected depth of the slot.
 8. Thecylinder lock of claim 6 wherein: the lock casing includes two pairs oflongitudinal tumbler-receiving cutouts, the pairs being respectivelyoffset by equal amounts on opposite sides of a central plane bisectingthe cylindrical bore of the casing; the rotatable tumbler retainersrotate concentrically about the axis of the cylindrical bore; and twokey-operated tumblers are slidably mounted in parallel relationshipwithin one rotatable retainer and are offset from the center of rotationof the retainer by an amount equal to the offset of thetumbler-receiving cutouts to register with the cutouts in a lockingposition of the retainer.
 9. The cylinder lock of claim 6 wherein: therotatable tumbler retainers are generally cylindrically shaped withaxially opposed end surfaces; and the camming portions of the rotatabletumbler retainers include triangularly shaped and axially extendingteeth and mating recesses on confronting end surfaces of the tumblerretainers.
 10. The cylinder lock of claim 9 wherein: the cam-engagingmeans includes a spring element for resiliently biasing the triangularlyshaped teeth into engagement with the mating recesses; and the endsurfaces of the tumbler retainers bearing the triangular teethadditionally include a tumbler-guiding groove extending transverse ofthe cylindrically shaped retainers and having a depth in the axialdirection completely accommodating the tumblers within the grooves belowthe end surfaces whereby the tumblers may slide freely within thegrooves of the retainer when the teeth are engaged with the matingrecesses.